1. 1. Dental Anatomy and Chronology Dr. Razan Ahmad Al Majali
2. 2. Tooth Morphology
3. 3. General informations Humans have two generations of teeth : deciduous and permanent By the age of 3 years all deciduous teeth have erupted . By 6 years, the first permanent teeth appear and hence the deciduous teeth are exfoliated one by one replaced by their permanent successors. A complete permanent dentition is present at around 18 years . 20 teeth 10 in each jaw. (primary dentition ) 32 teeth 16 in each jaw.
4. 4. Three basic tooth form : incsiform , caniniform , molariform . Incisors : cutting teeth , thin , blade- like crowns. Canines : piercing or tearing teeth , single pointed cone-shaped crown . Molars : grinding teeth possessing a number of cusps on an otherwise flattened biting surface . Premolars: bicuspid teeth ,replace the deciduous molars.
5. 5. Some terms for the description of tooth form : Crown : clinical crown : that portion of a tooth visible in the oral cavity Anatomical crown :that portion of a tooth covered with enamel . Root : clinical root : portion of tooth which lies within the alveolus . Anatomical root : that portion covered by cementum . Cervical margin : the junction of the anatomical crown and anatomical root . Occlusal surface : biting surface . Cusps : pronounced elevation of occlusal surface . Incisal margin :cutting edge Tubercle : small elevation on the crown . Cingulum : bulbous convexity near cervical region of the tooth .
6. 6. Ridge : linear elevation on the surface of a tooth. Marginal ridge : ridge at the mesial or distal edge . Fissure : long cleft between cusps or ridges . Fossa : rounded depression in a surface of a tooth . Buccal : toward cheeks. Labial : toward lips . Palatal : toward palate . Lingual : toward the tongue . Mesial : toward the median . Distal : away from the median .
7. 7. Dental notation: For deciduous teeth DI 2/2 DC 1/1 DM 2/2 = 10 For permanent teeth I 2/2 C 1/1 PM 2/2 M 3/3 =16 Zsigmondy system : 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 E D C B A A B C D E E D C B A A B C D E
8. 8. Federation Dentaire Internationale (FDI) : 1= max. rt. Quadrant 2= max. left quadrant for PERMANENT 3 = mand. Lft quadrant 4 = mand . rt quadrant 5= max. rt. Quadrant 6= max. left quadrant 7 = mand. Lft quadrant for DECIDUOUS 8 = mand . rt quadrant
9. 9. Differences between deciduous teeth and permanent : 1 . The deciduous teeth are smaller, although the mesiodistal dimension of the permanent premolars are generally less than those for deciduous molar . 2. Deciduous teeth have a greater constancy of shape . 3. The crown of deciduous teeth appear bulbous , often having pronounced labial or buccal cingula . 4. the cervical margins of deciduous teeth are more sharply demarcated and pronounced , enamel bulging rather than gently tapering . 5. the cusps of newly erupted deciduous teeth are more pointed .
10. 10. 6. the crowns of deciduous teeth have thinner enamel ( 0.5-1.0 mm ) than the crowns of permanent teeth (2.5 mm ) 7. the enamel of deciduous teeth are more opaque , gives the crown a whiter appearance 8. the enamel is softer and more easily worn in deciduous teeth . 9. enamel is more permeable in dec. teeth . 10. the aprismatic layer of surface enamel is wider in dec. teeth .
11. 11. 11. the enamel and dentine of ALL dec . teeth exhibit neonatal lines . 12. the roots of dec. teeth are shorter and less robust than those of permanent teeth . 13. the roots of dec. incisors and canines are longer in proportion to the crown than those of permanent ones. 14. the roots of the dec. molars are widely divergent extending beyond the dimensions of the crown. 15. the pulp chambers of dec. are proportionally larger in relation to the crown than those of permanent teeth. the pulp horns in dec. are more prominent. 16. the root canals of dec. are extremely fine . 17 . the dental arch for dec. dentition are smaller .
12. 12. A, The enamel cap of primary molars is thinner and has a more consistent depth. B, A comparatively greater thickness of dentin is over the pulpal wall at the occlusal fossa of primary molars. C, The pulpal horns are higher in primary molars, especially the mesial horns, and pulp chambers are proportionately larger. D, The cervical ridges are more pronounced, especially on the buccal aspect of the first primary molars. E, The enamel rods at the cervix slope occlusally instead of gingivally as in the permanent teeth. F, The primary molars have a markedly constricted neck compared with the permanent molars. G, The roots of the primary teeth are longer and more slender in comparison with crown size than those of the permanent teeth. H, The roots of the primary molars flare out nearer the cervix than do those of the permanent teeth.
13. 13. THE INCISORS : THE MAXILLARY FIRST CENTRAL PERMANENT INCISOR : Incisal view : - The crown and incisal margin are centrally positioned over the root of the tooth. - The incisal margin presents as narrow flattened ridge rather than as a fine sharp edge. - The crown outline is bilaterally symmetrical, being triangular. Mesial appears slightly larger. - may have two grooves, the labial lobe grooves; correspond to three developmental lobes (mammelones) which are lost by attrition.
14. 14. Labial view : Smooth , convex . Convexity marked cervically . flat at the middle and incisal regions. Crown length almost as great a root length . Two faint grooves which are extensions of the labial lobe grooves. Mesial surface is straight and at right angle to incisal margin . Distal outline is convex and the distoincisal angle is more rounded.
15. 15. Palatal view : More irregular ,shovel shaped Bordered by mesial and distal marginal ridges . Middle and incisal third being concave. Prominent cingulum lies near the cervical margin maybe single ,divided
16. 16. Mesial and distal : Wedge shaped or triangular . The root : Single root tapers toward the apex . The root is conical in cross section , narrower palataly .
17. 17. THE MAXILLARY PERMANENT LATERAL INCISOR : The smallest mesiodistal dimensions of any teeth in permanent dentition. One of the most variable teeth in dentition . It is morphologically a diminutive form of maxillary incisor with slight modifications . The crown is much narrower and shorter , the crown:root ratio is decreased .
18. 18. Incisal aspect : More rounded than central. Labial view : The mesioincisal and distoincisal angles and mesial and distal crown margins are more rounded .
19. 19. Palatal view : Similar to central . marginal ridges and cingulum are more pronounced , and palatal concavity appears deeper. In front of the cingulum is a pit ( foramen caecum)that may extend into the root. The root : Slightly compressed and grooved on the mesial and distal surfaces . CAN BE DISTINGUISHED : by their size , the marked lingual inclination of the crowns over the roots , mesiodistal compression of their roots , poor development of the marginal ridges and cingula .
20. 20. THE MANDIBULAR PERMANENT CENTRAL INCISOR : Incisal view : Bilaterally symmetrical triangular shape . Labial view : The crown is almost twice as long as it is wide . Straight incisal angle . Mesio and distoincisal angles are sharp and approximately at right angle . Mesial and distal surfaces are similar , being flattened in the middle and cervical thirds and convex in the incisal third .
21. 21. Lingual view : Smooth and slightly concave Lingual cingulum and mesial and distal marginal ridges are less distinct . Mesial and distal view : Wedge shape . The cervical margin on the distal side is less curved than that of the mesial . The root : Narrow , conical . Frequently grooved on the mesial and distal surfaces , distal groove more marked and deeper .
22. 22. THE MANDIBULAR LATERAL PERMANENT INCISOR : Closely resembles the mand. Central incisor . Slightly wider mesiodistally and asymmetric in shape. Distal surface diverges , giving it a fan- shaped apperance . Distoincisal angle more acute and rounded . DISTINGUISHING characteristic : the angulation of the incisal margin relative to the labiolingual axis of the root is twisted distally in a lingual direction , where as in the central it forms a right angle .
23. 23. THE CANINES: The only teeth in the dentition with a single cusp . Triangle.. mesially and distally Trapezoidal .. buccally and palataly ..
24. 24. THE MAXILLARY PERMANENT CANINE : Well developed cingulum and the longest root of any tooth. Incisal view : The distal portion is much wider than the mesial portion. The pointed shape of the canine is thought to be related to an increase in the size of a central mammelon Prominent longitudinal ridges pass from the cusp tip down both the labial and palatal surfaces. Variations : like an accessory
25. 25. Labial view : Marked by longitudinal ridge extends from the cusp to the cervical margin . The incisal part occupies at least 1/3 of the crown height . The mesial arm is shorter than the distal arm. The distoincisal angle is more rounded. The mesial profile is slightly convex with a straight line with the root . the distal is markdly convex an obtuse angle with the root .
26. 26. Palatal view : Well defined cingulum and distinct marginal ridges . Longitudinal ridge meets the cingulum and is separated from the marginal ridges by a distinct groove or fossa Mesially and distally : Great width of the cervical third of both the crown and the root . The curvature of cervical margin distally is less marked than mesially.
27. 27. The root : The largest and stoutest in the dentition. Triangular in cross section . Mesial and distal surfaces of the root are often grooved longitudinally.
28. 28. THE MANDIBULAR CANINE : Similar to the maxillary , but smaller , more slender , more symmetrical . The cusp is less developed . with attrition it may resemble max. lateral incisor. Incisal view : No distinct longitudinal ridges from the tip of the cusp onto the labial and lingual surfaces .
29. 29. Labial view : The cusp is less pointed , the incisal margin occupies only 1/5 of the crown height . Crown is narrower mesiodistally , it appears longer , narrower and more slender . Mesial and distal profiles are parallel. Lingual view : Surface of cingulum ,marginal ridges and fossa are indistinct . Lingual surface is flatter than
30. 30. Mesially and distally : Wedge-shaped appearance . Cervical margin follows a course similar to the incisors , more marked distally . The root : Normally single .occasionally it may bifurcate . Oval cross section . The root is grooved
31. 31. THE PREMOLARS : Bicuspids ( two cusps buccal and lingual separated by mesiodistal occlusal fissure). To distinguish upper and lower premolar when viewed mesially or distally upper premolars are trapezoidal in shape while the lowers are rhomboidal in shape and inclined lingually .
32. 32. THE MAXILLARY FIRST PREMOLAR : Occlusal view : Ovoid . border buccaly than palatally Mesio and distobuccal corners are less rounded than mesio and distopalatal . Distinct mesial and distal marginal ridges. Central occlusal fissure that crosses mesial marginal ridge onto mesial
33. 33. Maxillary first premolar, occlusal aspect. TBC, Tip of buccal cusp; MBCR, mesiobuccal cusp ridge; MBDG, mesiobuccal developmental groove; MTF, mesial triangular fossa; MMDG, mesial marginal developmental groove; MMR, mesial marginal ridge; MLCR, mesiolingual cusp ridge; LTR, lingual triangular ridge; TLC, tip of lingual cusp; CG, central groove; DLCR, distolingual cusp ridge; DMR, distal marginal ridge; DTF, distal triangular fossa; DBDG, distobuccal developmental groove; BTR, buccal triangular ridge; DBCR, distobuccal cusp ridge.
34. 34. Buccal view : Resemble the canine . Longitudinal ridge . Prominent mesio and disto- occlusal angles . Mesial slope is longer than distal slope . Palatal view : Palatal cusp is smaller and lower than buccal . The tip lies more mesially .
35. 35. Mesial view : Canine groove across the mesial marginal ridge . Cervical third marked by a distinct concavity the canine fossa Distal veiw : Lacks the canine groove and fossa . The roots : Usually two roots , sometimes single root which is deeply grooved .
36. 36. THE MAXILLARY SECOND PREMOLAR : Similar to first premolar except : Occlusally : More rounded mesio distobuccal corners. Mesial and distal profiles parallel to each other . Smaller mesiodistally. Central fissure doesnt cross the marginal ridge.
37. 37. Buccally : Less prominent disto and mesio-occlusal angles. narrow shouldered appearance Smaller cusps , equal in size cusps. Mesially : No canine fossa and groove . The root : Single root .
38. 38. THE MANDIBULAR FIRST PREMOLAR : Smallest premolar . Dominant buccal cusp and very small lingual cusp. Occlusal view : More than 2/3 of buccal aspect is visible. Diamond shaped. Broad buccal cusp , its apex at midpoint of the crown. Buccal and lingual cusps are connected by a transverse ridge that divides the occlusal fissure to mesial and distal fossa ( mesial fossa is smaller). Canine groove crosses the mesial marginal ridge .
39. 39. Buccally : nearly Symmetrical . lingual view : the entire buccal profile and occlusal surface are visible . 2nd premolar differs from other premolars that the occlusal plane doesnt lie perpendicular to the long axis of the tooth . The root : Single , conical ,and oval cross section . Root is grooved longitudinally mesial and distal .
40. 40. THE MANDIBULAR 2nd PREMOLAR : The crown is generally larger. Lingual cusp is better developed. Occlusal aspect : Round or square . Well defined mesiodistal occlusal fissure . Distal fossa is larger then mesial fossa. Accessory cusplets are common on both buccal and lingual . Lingual cusp is usually subdivided to mesio and distolingual cusps. Mesiolingual is wider and higher .
41. 41. Buccal aspect : Symmetrical . Appears shorter and more rounded than 1st mand premolar . Lingually : Little if any of the occlusal surface and buccal profile is visible . Mesial and distal : Mesial marginal ridge is higher than the distal . Occlusal surface appears horizantal to the long axis . The root : Single , conical , nearly round in cross section.
42. 42. THE MOLARS : largest occlusal surfaces of all teeth . have 3-5 MAJOR cusps. Have more than one buccal cusp . In general .. 3 roots upper , 2 roots lower . Buccally and lingually are trapezoidal. Mesially and distally .. upper trapezoidal , lower rhomboidal.
43. 43. MAXILLARY 1st PERMANENT MOLAR : Occlusally : Rhombic in outline. Four major cusps separated by an irregular H- shaped occlusal fissure. Occlusal table is divided to two components (trigon and talon )by the oblique ridge. Oblique ridge passes from the mesiopalatal cusp to the distobuccal cusp. Mesiopalatal .. the largest cusp Trigon ; triangular in shape ,apex directed palataly . bears the mesiobuccal ,mesiopalatal, and distobuccal cusps . Apex: mesiopalatal base : buccal cusps Mesial marginal ridge and the oblique ridge form its sides. Central fossa , central fissure terminate in mesial pit , buccal fissure,
44. 44. Talon : bears distopalatal cusp .the smallest cusp Distopalatal fissure separates the palatal cusps ,ends in a distal pit. Accessory cusplet the tubercle of Carabelli : seen on mesiopalatal cusp ,variable sizes,found on 60% of max 1st molars. CHARACTERISTIC of max. molar : the tips of palatal cusps are nearer the mid- mesiodistal diameter of the crown than buccal cusps.
45. 45. Maxillary right first molar, occlusal aspect. MBCR, Mesiobuccal cusp ridge; CF, central fossa (shaded area); MTF, mesial triangular fossa (shaded area); MMR, mesial marginal ridge; MLCR, mesiolingual cusp ridge; OR, oblique ridge; DLCR, distolingual cusp ridge; DF, distal fossa; DTF, distal triangular fossa (shaded area); DMR, distal marginal ridge; DBCR, distobuccal cusp ridge.
46. 46. Buccal view : Mesiobuccal cusp is wider than distobuccal . but equal in heights . Buccal groove extends to end about half way . Distal profile.. convex all regions . mesial profile concave in cervical 1/3 and convex n the middle and occlusal thirds . Palatal view : Mesiopalatal is larger , blunt . Palatal groove extends approximately halfway up the palatel surface.
47. 47. Mesial and distal : Maximum bucco-palatal dimension is at the cervical margin. Mesial marginal ridge is more prominent and have a no. of destinct tubercles which are rare distally. The roots: 3 roots : 2 buccaly , 1 palataly .from a common root stalk . At the root stalk palatal root is more related to distobuccal root . Palatal is the longest and strongest. Buccal roots are more slender and mesiodistally flattened .
48. 48. THE 2nd MAXLLARY MOLAR : Resembles 1st molar but shows some reduction in size and cusps relationship. Common variations in morphology . Occlusal view : More pronounced rhomboid form. Smaller oblique ridge , the talon is reduced. More variable occlusal fissure pattern.
49. 49. Buccal view : Two features that differentiate the 2nd molar : smaller size and distobuccal cusp . Palatal view : Reduction in size of the distopalatal cusp is more visible. Tubercle of Caraballi is not always found.
50. 50. Mesial and distal : The tubercles on marginal ridges are less pronounced. The roots : 3 roots , shorter and less divergent, maybe partly fused. Apex of mesiobuccal root is in line with the center of the crown . while in 1st molar is in line with the tip of mesiobuccal cusp.
51. 51. THE MAXILLARY 3rd MOLAR : Most variable in dentition . Most often absent congenitally. Most commonly , the crown is triangular in shape having cusps of trigon but no talon. Roots are often fused and irregular in form .
52. 52. MANDIBULAR MOLARS : Differences with the upper : 1. Mand. Molar have two roots ,mesial and distal . 2. Derived from a five cusped form. 3. Are oblong , broader mesiodistally than buccolingually . 4. The fissure pattern is cross-shaped. 5. Lingual cusps are more equal size. 6. The tips of buccal cusps are shifted lingually ,the whole buccal surface is visible occlusally.
53. 53. THE MANDIBULAR 1st MOLAR : Pentagonal in outline. Occlusal view : Occlusal surface is divided into buccal and lingual by a mesiodistal occlusal fissure. Buccal side three distinct cusps : mesiobuccal ,distobuccal , and distal . rounded cusp tips displaced lingually rounded and lower than lingual cusps . Lingual side two cusps :mesiolingual , distolingual . large and pointed . Smallest cusp is the distal
54. 54. 90% of cases mesiolingual and distobuccal are joined across the floor of the central fossa . this feature and the five cusped pattern is termd dryopithecus pattern. dryopithecus pattern sometimes referred to Y5 due to Y-shaped tissue pattern with 5 cusps.
55. 55. Mandibular right first molar, occlusal aspect. DBCR, Distobuccal cusp ridge; DBDG, distobuccal developmental groove; DCR, distal cusp ridge; DTF, distal triangular fossa (shaded area); DLCR, distolingual cusp ridge; LDG, lingual developmental groove; MLCR, mesiolingual cusp ridge; MTF, mesial triangular fossa (shaded area); SG, a supplemental groove; MBCR, mesiobuccal cusp ridge; MBDG, mesiobuccal developmental groove.
56. 56. Buccal view : Three cusps , distal cusp is the smallest . buccal surface is markedly convex especially at cervical third. Lingual view : Mesiolingual cusp appears slightly larger. Fissure separating the two cusps doesnt extend significantly to lingual surface. Surface convex then flat or concave cervically.
57. 57. Mesially and distally : Mesial and distal marginal ridges appear V-shaped . Distal surface is more convex . The roots : Two roots ,mesial and distal . arise from common root stalk. Mesial root is usually deeply grooved. Both roots curve distally.
58. 58. THE MANDIBULAR 2nd MOLAR : Occlusal view : Rectangular . buccal equal to lingual . Four cusps , mesial cusps are slightly larger than distal cusps . Cusps separated by a cross shaped groove , complicated by supplementary grooves . Buccal ; Smaller than 1st molar. Buccal surface is highly convex .
59. 59. Mesial and distal : The proximal surfaces have more equal convexity. The roots : Smaller , less divergent , partly fused . Distal inclination is more marked.
60. 60. THE MANDIBULAR 3rd MOLAR : Variable morphology . not as variable as the max. 3rd molar . Usually 4-5 cusps . rounded rectangle . Very irregular occlusal pattern. Roots greatly reduced in size , more fused , marked distal inclination .
61. 61. PULP MORPHOLOGY
62. 62. MAX. PERM. CENTRAL INCISOR : Labial aspect : Pulp chamber follows the outline of the crown . In young tooth , pulp chamber has three pulp horns correspond to the mammelones. Distally : Pulp tapers towards the incisal edge and widen cervically. Cross section : Ovoid ,becomes round as it nears the apex. With age : Reduced dimensions of the pulp chamber and root canal . Pulp chamber recedes and may disappear completely .
63. 63. MAX. LATERAL PERM. INCISOR : Similar to central but smaller. Root canal is single , slightly ovoid , commonly curves both distally and palataly.
64. 64. MAND. PERM. CENTRAL INCISOR : Pulp chamber is similar to max. central , but much smaller . Pulp chamber is oval in cross section. Root canal is ovoid in cross section. 30% have two canals , most of them fuse near the apex and exit by single foramen.
65. 65. MAND. LATERAL INCISOR : Tooth and root canal are larger than central. 43% two root canals more common than cental . Exit by separate foramina.
66. 66. CANINES : MAX. CANINE : Narrow pulp chamber with a single pulp horn points cuspally . Pulp chamber and single canal are wider labiopalataly than mesiopalatly. Root canal doesnt constrict markedly until apical third . Root canal are ALWAYS single .
67. 67. MAND. CANINE : Pulp cavity resembles max. canine but smaller in all dimensions . 6% have two root canals usually with separate foramina.
68. 68. PREMOLARS : MAX 1ST PREMOLAR : 85% has two roots , sometimes fused. The two canals exit by separate foramina . Less than 10% ,single root with single root canal . 5% have three canals (sometimes in three roots ). Two distinct pulp horns pointing towards the cusps. Pulp chamber is closest to the surface mesially . In cross section root canals are generally round.
69. 69. MAX. 2ND PREMOLAR : 75% single root with single root canal . If two canals are present , mostly they have separate apical foramina. In cross section the root canal is oval .
70. 70. MAND. 1ST PREMOLAR : Pulp chamber is wider buccolingually . like max. premolar Usually only one pulp horn extends into buccal cusp. unlike max. premolar . 75% single root canal . Most teeth that have two canals have two apical foramina .
71. 71. MAND. 2ND PREMOLAR : 85% have single canals . and usually two well developed pulp horns pointing towards the cusps.
72. 72. MOLARS: MAX. 1ST PERM. MOLAR : pulp chamber is rhomboidal in shape , wider buccopalatally. Four pulp horns , one to each major cusp. The pulp horn to mesiobuccal cusp is the longest . The floor lies below cervical margin . Three root canals . or four canals on 60% ( 4th canal in the mesiobuccal root ). 2/3 of the 4th canals rejoin the main canal of the mesiobuccal root near apex. Palatal root canal is the widest and longest . Floor of the chamber is marked by series of developmental grooves that join the orifice of the root canals.
73. 73. MAX. 2ND MOLAR : Similar to 1st molar pulp cavity but smaller with the rhomboidal shape more compressed. Roots are more convergent. Orifices are closer together. Roots are commonly fused. 2nd mesiobuccal canal is less common ( 40% of cases ).
74. 74. MAND. 1ST MOLAR : Pulp chamber is wider mesiodistally than buccolingually . wider mesially than distally. Five pulp horns pointing to the cusps. Lingual pulp horns are longer and more pointed. Floor of chamber lies at or below the level of cervical margin . The mesial root has two root canals (mesiobuccal and mesiolingual). Both are circular in cross section. 30% of teeth the distal root has two canals
75. 75. MAND. 2ND MOLAR : Pulp chamber closely resembles 1st molar. But it has only four pulp horns. Only rarely (8% of cases)two canals in distal root.
76. 76. PULP CHAMBERS IN DECIDUOUS TEETH :
77. 77. The chamber is relatively larger and the pulp horns longer and closer to the surface of the tooth. All incisors and canines have single canals . 10% on mand. Incisor there are two canals . Pulp chamber of deciduous mand molar are proportionally larger than those of max. molars. The mesiobuccal pulp horn is near the occlusal surface and highly vulnerable to exposure . Small canals from the floor to the furcation region are common. Severe curvature of deciduous teeth.
78. 78. Features to bear in mind : - Maxillary D has 2-4 roots canals (75% 2 canals in the mesiobuccal root and palatal and distobuccal roots . - Maxillary E has 2-5 root canals (90% of cases mesiobuccal root contains two canals) , (palatal and distobuccal roots sometimes fuse and contain a single common canal . - Mandibular D may have 2-4 canals ( 75% of mesial roots have two canals , and 25% of distal). - Mandibular E usually has 3 canals (but vary 2-5) (85% of mesial roots , 25% of distal roots have two canals ).
79. 79. DECIDUOUS TEETH :
80. 80. Upper A : No mammelons are seen on the incisal margin . Cingulum is very prominent . Marginal ridges are poorly defined . Cervical margins are pronounced but less sinuous than permanent teeth. Compared with permanent incisor , the root is longer in proportion to the crown.
81. 81. Upper B : Similar to A , one obvious difference is the more acute mesioincisal angle and more rounded distoincisal angle. Palatal surface is more concave , marginal ridge more pronounced .
82. 82. Lower A : Similar to permanent . however ,its much shorter . No mammelon grooves . Lingual cingulum and marginal ridges are poorly defined. More rounded root , tends to incline distally .
83. 83. Lower B : The mesioinciasal angle is more obtuse and rounded than lower A Distoincisal angle is markedly rounded , it distinguishes it from upper B . Unlike the permanent , the root is rounded .and its longer than lower A .
84. 84. Upper C : Similar to permanent ,but more bulbous . Generally symmetrical , but if there is asymmetry the mesial slope tends to be longer than distal slope. The width of the crown is greater than the length. Longitudinal ridges on the labial and palatal surfaces .it divides the palatal surface into two shallow pits. Marginal ridges are indistinct . The root is long compared with the crown height. triangular in cross section .
85. 85. Lower C : More slender than upper C . The crown is asymmetrical , the cusp tip displaced mesially. Poorly developed longitudinal ridges on labial and lingual surfaces . The width of the crown is less than the length . Root is triangular in cross section .
86. 86. Upper D : Most atypical of all molars , primary and permanent . Its the smallest molar . Occlusally : - Irregular quadrilateral .buccal and palatal parallel. - Mesiobuccal angle is extended to produce a prominent bulge , the molar tubercle. - Mesiopalatal angle is obtuse. - Generally its a bicuspid tooth . buccal and palatal . - Buccal cusp is divided by shallow buccal fissure into two , mesial part is larger. - Palatal cusp may also be subdivided into two . - Tips of the cusps converge towards the midline .
87. 87. Buccal aspect : - Height less than width . - On mesial side lies the buccal cingulum. Mesial and distal : - Cervical bulbosity of the buccal and palatal surfaces . - Prominent molar tubercle mesially . - No fissure crosses the marginal ridges . The roots : - Three roots ( two buccal and one palatal ) arise from a common root stalk . - The palatal root is the largest. - The distobuccal and palatal roots maybe partly fused .
88. 88. Upper E : Resembles the max. permanent first molar . Size , whiteness , widely diverging roots and low buccal cingulum distinguish it . A tubercle of Carabelli is often well developed.
89. 89. Lower D : Occlusally : - Irregular quadrilateral with parallel buccal and lingual surfaces . Elongated mesiodistally. - Mesiobuccal corner is extended forming a molar tubercle . mesiolingual is obtuse . - Buccal and lingual part . mesiodistal fissure . - Buccal part has two cusps , mesiobuccal is larger . - Lingual part narrower , two cusps separated by lingual fissure . mesiolingual is larger. - Transverse ridge connect the mesial cusps , form a distal fissure and a mesial pit. - Supplemental groove extends over mesial marginal ridge .
90. 90. Buccal aspect : - The mesiobuccal cusp occupies 2/3 of the crown. - The profile of mesial is flat and distal is convex . Mesially and distally : - Buccal and lingual aspects converge toward the midline . The roots : - Two divergent roots . mesial and distal . - Mesial root is often grooved .
91. 91. Lower E : A small version of lower first permanent molar . Narrower , whiter , widely diverging roots. The mesiobuccal corner of the crown ,the greater convexity of the mesial and distal surfaces . The mesiolingual and distobuccal cusps are not usually joined to give the Dryopithecus pattern .
92. 92. ETHIC AND RACIAL DIFFERENCES IN TOOTH MORPHOLOGY